1. Field of the Invention
This invention relates in general to composite tape technology, and especially to machines and methods for laying composite tape to form laminated structural members.
2. Description of the Prior Art
Composite tapes of tectonic unidirectional filaments in a resinous matrix are used to form structural members. Some aircraft have polymerized laminations of such tapes used as portions of the horizontal and vertical stabilizer skins instead of the more conventional metallic skins. The composition of the suitable tapes, the filaments and matrices are well known in the aerospace arts.
Composite tapes may be laid by hand into parallel rows to form one layer and crossing parallel rows to form additional layers. Machines to automate the process have been suggested, one being disclosed in U.S. Pat. No. 3,574,040, "Apparatus For Making Laminated Structural Shapes By The Controlled Detrusive Placement And Polymerization of Tectonic Filamentous Tapes", B. E. Chitwood, et al., Apr. 6, 1971. This machine employs a belt drive to pull composite tape from a spool, a separator to collect the backing from the tape, a tape shear blade, an applicator vacuum belt to carry the tape to the work structure, and a pendant roller foot including heating elements to assure adhesion to the preceding layer by imparting tackiness to the resinous matrix and partial polymerization to the semi-cured stage.
In an alternate embodiment the heating of the tape is accomplished with a detrusion nozzle for directing heated air onto the tape. Gap or overlap of adjacent tapes is avoided by use of a sensor such as a photoelectric cell or air-gauge to detect the edge of a previously laid tape for communication to the control system.
The system includes a frame to support a table, a rotary table to support a pattern or die, a trellis, a tram carriage on a rail beam to support a detrusion pendant containing the above tape laying mechanisms. Control of the tape laying mechanism is achieved by the use of a master indexing template on a rotary table and photo electric scanning cells, which sense the pattern of the tape from the template and transmit this information to the tape laying mechanism. There have been various modifications to this machine such as the use of numerical control instead of the template.
The prior art methods and mechanisms have the following disadvantages: (1) the tape shear blade cannot cut tape at angles greater than about sixty degrees and cannot make curved or bi-directional cuts; (2) the tape shear blade cannot cut tape while the tape is being fed through the machine; (3) short courses or lengths of tape less than 93/4" cannot be laid; and (4) the pressing roller cannot terminate its pressing along a nonperpendicular cut.